MODULE cov_cutoff_mod

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Overview

Computes the weight with which an observation should impact a state variable that is separated by a given distance. The distance is in units determined by the location module being used.

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NAMELIST

This namelist is read from the file input.nml. Namelists start with an ampersand '&' and terminate with a slash '/'. Character strings that contain a '/' must be enclosed in quotes to prevent them from prematurely terminating the namelist.

&cov_cutoff_nml
   select_localization = 1  
/

Item	Type	Description
select_localization	integer	Selects the localization function. 1 = Gaspari-Cohn 5th order polynomial with halfwidth c. 2 = Boxcar with halfwidth c (goes to 0 for z_in < 2c). 3 = Ramped Boxcar. Has value 1 for z_in < c and then reduces linearly to 0 at z_in = 2c.

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OTHER MODULES USED

types_mod
utilities_mod
location_mod

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PUBLIC INTERFACES

use cov_factor_mod, only :

comp_cov_factor

A note about documentation style. Optional arguments are enclosed in brackets [like this].

var = comp_cov_factor(z_in, c [, obs_loc] [, obs_type] [, target_loc] [, target_kind] [, localization_override])

real(r8)                                  :: comp_cov_factor
real(r8), intent(in)                      :: z_in
real(r8), intent(in)                      :: c
type(location_type), optional, intent(in) :: obs_loc
integer, optional, intent(in)             :: obs_type
type(location_type), optional, intent(in) :: target_loc
integer, optional, intent(in)             :: target_kind
integer, optional, intent(in)             :: localization_override

Returns a weighting factor for observation and a target variable (state or observation) separated by distance z_in and with a half-width distance, c. Three options are provided and controlled by a namelist parameter. The optional argument localization_override controls the type of localization function if present. The optional arguments obs_loc, obs_type and target_loc, target_kind are not used in the default code. They are made available for users who may want to design more sophisticated localization functions.

var	Weighting factor.
z_in	The distance between observation and target.
c	Factor that describes localization function. Describes half-width of functions used here.
obs_loc	Location of the observation.
obs_type	Observation specific type.
target_loc	Location of target.
target_kind	Generic kind of target.
localization_override	Controls localization type if present. Same values as for namelist control.

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FILES

filename	purpose
input.nml	to read cov_cutoff_nml

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REFERENCES

Gaspari and Cohn, 1999, QJRMS, 125, 723-757. (eqn. 4.10)

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ERROR CODES and CONDITIONS

Routine	Message	Comment
comp_cov_factor	Illegal value of "select_localization" in cov_cutoff_mod namelist	Only values 1 through 3 select a localization function.

KNOWN BUGS

none at this time

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FUTURE PLANS

none at this time

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PRIVATE COMPONENTS

N/A

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Terms of Use

DART software - Copyright UCAR. This open source software is provided by UCAR, "as is", without charge, subject to all terms of use at http://www.image.ucar.edu/DAReS/DART/DART_download

Contact:	DART core group
Revision:	$Revision$
Source:	$URL$
Change Date:	$Date$
Change history:	try "svn log" or "svn diff"